This invention relates to the drilling of oil and gas wells, offshore and onshore, and is particularly directed to a method and apparatus which is an improvement of, or an alternate to, as the case may be, the side drive drilling apparatus and method of the Krasnov application, supra.
The side drive drilling system of the Krasnov application, which facilitated handling, drilling with triple pipe sections (approximate 90 foot lengths), and back reaming, has essentially the following features:
1. an elongated, axially stationary, drive shaft, referred to as a "kelly" therein, extending essentially the height of the derrick and rotated by a motor located near the platform level,
2. the drive shaft is located to one side of and substantially parallel to the main or drilling axis in the derrick,
3. a bushing driven by the drive shaft, as part of the drive assembly for the drilling unit, movable vertically on the drive shaft and rotated thereby,
4. a rail system: for guidance of the drilling unit as it moves vertically for drilling and reaming, and
5. apparatus to facilitate handling heavy casing.
The apparatus and method of this invention, in its preferred embodiment, comprises a side drive system with a vertical drive shaft driven from the platform level and powering a drilling unit for rotating drill pipe. Except for the tethering of the drive shaft at the top of a derrick and its coupling to a power source at the platform or drill floor level, there is no stabilizing means for the system. Thus, the preferred embodiment of this side drive system has the following features and available options:
1. all the features of the side drive drilling system of the Krasnov application, supra, but without the guide rails of the Krasnov system;
2. utilizes the conventional rotary table as the power source (lower drive assembly) for rotating the drive shaft;
3. utilizes a hollow drive shaft to increase the lateral natural frequencies of the drilling system;
4. utilizes a torque balanced upper drive assembly to minimize unequal forces and torques imparted to the drive shaft that would cause excessive shaft deflections; and
5. may use a stabilizing system for the drilling unit or the drive shaft itself as an option.
In either the side drive system of the Krasnov application, supra, or the side drive system of this invention, the gate valve of the Krasnov application and or/the easy break-out tool of the Goris and Krasnov application may be used as still other options in practicing this invention.